A diaphragm setting ring disclosed in Japanese Laid-open Utility Model Application No. 1979-72039 and a click stop mechanism disclosed in Japanese Laid-open Patent Application No. 1986-173227 are conventionally known examples of a diaphragm setting ring rotatably mounted on a stationary tube of a lens barrel to adjust a lens aperture and a diaphragm device of a lens including a click mechanism capable of stopping such a diaphragm setting ring at positions corresponding to a plurality of aperture numbers with click action, respectively.
The diaphragm setting ring described in Japanese Laid-open Utility Model Application No. 1979-72039 has a plurality of click stock grooves formed in a curved inside surface of the diaphragm setting ring at specific intervals along a circumferential direction of the curved inside surface and a click ball disposed on a curved outside surface of the stationary tube facing the curved inside surface of the ring, the click ball being forced outward by a leaf spring. The diaphragm setting ring thus configured makes it possible to take a picture at one of lens apertures defined at individual stop positions. Also, the click stop mechanism described in Japanese Laid-open Patent Application No. 1986-173227 has a plurality of click grooves formed in a curved inside surface of a diaphragm preset ring at specific intervals along a circumferential direction and a click ball disposed on a stationary ring facing the curved inside surface of the diaphragm preset ring, the click ball being forced outward by a leaf spring. In this click stop mechanism, the click ball is pressed against the curved inside surface of the diaphragm preset ring.